The background information discussed below is presented to better illustrate the novelty and usefulness of the present invention. This background information is not admitted prior art.
In the petroleum industry, a variety of methods are used for extracting oil from underground reservoirs. Perhaps one of the most common of these methods is an oil well pumping unit known as the “walking beam” or “pump-jack” type. These pump-jack pumping units, also called nodding donkey, pumping unit, horsehead pump, rocking horse, beam pump, dinosaur, sucker rod pump (SRP), grasshopper pump, thirsty bird, jack pump, popping johnny or walking beam pump (collectively referred to herein as pump-jack or pump-jacks) is the overground drive for a reciprocating piston pump down-hole in an oil well. Pump-jacks are typically used to mechanically lift liquid out of the well if there is not enough bottom-hole pressure for the liquid to flow all the way to the surface. A pump-jack converts the rotary mechanism of a motor to a vertical reciprocating motion to drive the pump shaft, and is exhibited in the characteristic nodding motion.
Modern pump-jacks are powered by a prime mover. This is may be an electric motor, but internal combustion engines are used in isolated locations without access to electricity. Common off-grid pump-jack engines run on casing gas produced from the well, but pump-jacks have been run on many types of fuel, such as propane and diesel. In harsh climates such motors and engines may be housed in a shack for protection from the elements.
The prime mover of the pump-jack runs a set of pulleys or sheaves, via a belt, to the transmission or gear-box which drives a pair of cranks, generally with counterweights on them to assist the motor in lifting the heavy string of rods. The cranks raise and lower one end of an I-beam, or pump arm, which is free to move on an A-frame. On the other end of the beam, there is a curved metal box called a Horse Head or Donkeys Head, so named due to its appearance. A cable made of steel or fiberglass, called a bridle, connects the horse head to the polished rod, a piston that passes through the stuffing box down the well to actuate the down-hole pump. The polished rod has a close fit to the stuffing box, letting it move in and out of the tubing without fluid escaping. The bridle follows the curve of the horse head as it lowers and raises to create a nearly vertical stroke. The polished rod is connected to a long string of rods called sucker rods, which run through the tubing to the down-hole pump, usually positioned near the bottom of the well.
In the course of regular maintenance or modification of a pump-jack, the pump arm is typically operated through its up-down cycle until the pump arm brings the pump head down to its lowest position, closest to the ground. At this point the unit is stopped and a safety hand brake may be applied. Typically the safety brake is attached to an axle that is common to the pulley or sheave on the gear box (i.e. with the sheave on one side of the gear-box and the brake attached to the axle at the other side of the gear-box). However, such a brake is normally a drum brake which relies on friction to prevent the various (heavy) components of a pump-jack from moving. Such drum brakes are known to slip, thereby creating a safety hazard. As such, in current practice, a chain may also be passed over the pump arm, and/or through the sheave at the gear-box, and then secured to the platform or base of the pump unit using a boomer.
The addition of this secured chain provides some added degree of safety, should the brake mechanism fail, because it does not rely on friction but, rather, locks the moving component directly. However, this method of using a chain also has disadvantages including: (i) that an operator has to enter physically close to the pump-jack to apply the chain, thereby placing him or herself inside the rotation area, which area is often fenced off or enclosed for safety reasons because of the heavy weights and large moving equipment involved; and (ii) that a chain through the sheave and then secured to the base will impede or prevent replacement of the belt, should such replacement be part of the pump-jack maintenance.
Therefore, what is needed is a safety device for a pump-jack that does not rely on friction to stop the moving component(s) of a pump-jack and which can be actuated to lock and unlock the pump-jack remotely, i.e. from outside the rotation area.